Synthesizer for sound or voice reproduction



F. VILBIG May 21, 1957 SYNTHESIZER FOR SOUND OR VOICE REPRODUCTION Filed Dec. 4; 1953 4 Sheets-Sheet l Mmm.

F. VlLBlG May '21, 1957 I SYNTHESIZER FOR SOUND OR VOICF REPRODUCTION Filed Dec. 4, 19'53\ 4 Sheets-Sheet 2 F. VILBIG May 2l, 1957 SYNTHESIZER FOR SOUND OR VOICE REPRODUCTION 4 Sheets-Sheet 3 INVENTOR.

Filed Dec. 4, 1953 lfrazMf/f May 21., 1957 F. vlLBlG 2,793,249.

SYNTHESIZER FOR SOUND OR VOICE REPRODUCTION Filed Dec. 4, 195; 4 she'ets-sheet 4 irmeyfgg* United. States l SYNTHESIZER FOR SOUND OR VOICE REPRODUCTION Friedrich Vilbig, Cambridge, Mass., assignor to the United States of America as represented by the Secretary of the Air Force The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a vocoder system, the word vocoder being a contraction of voiceecoder, but relates more specifically to the synethesizer component of the vocoder system.

The transmission of speech or other like sounds require frequency bands of some thousand cycles per second band width.l This great band width has an unfavorable action in many respects. With radio transmitters, for example, the available wave bands are but poorly utilized and, in addition, the influence of atmospheric disturbances is great because these disturbances increase as the square root of the band width. For this reason there has been considerable research on the problem of considerably decreasing the band Width during transmission. One of the most familiar methods for doing this is the vocoder. The structure and operation of the vocoder is very completely discussed in the article entitled, Analysis-synthesis telephone, with special reference to the vocoder, by R. I. Halsey, BSc. (Eng), Member, and J. Swaffield, Ph. D., Associate Member, in The Journal of the Institution of Electrical Engineers, volume 95, part III, No. 37, September 1948, pages 391. to 405, inclusive. The vocoder shown and described in the above-mentioned article is a basic idea of great merit and value in voice and sound transmission but it has the disadvantage of being very bulky and weighty in that it has many separate elements as, for example, thirty band-pass filters, ten modulators, a relaxation oscillator, and a hiss generator, among other elements, which restricts its use to permanent stations.

In the present invention the bulk and weight of the vocoder may be greatly reduced by utilizing a particular synthesizer component particularly shown and described herein. The particular synthesizer is composed primarily of a special tube, a modulation disk, and a photocell tube which are used to replace a relaxation oscillator, a hiss generator, ten modulators, and 20 band-pass filters in the known vocoder synthesizer. The special tube produces ten`s'treaks of light, one for each frequency band, which are established by the modulation disk. The special tube has an electrostatic arrangement therein to control the frequency level of the fundamental frequency and -all harmonics in accordance with the voice pitch channel of 2,793,249 .e Patented Mayu-.21, 1957 voice and sound transmission which is suiiiciently compact and light in weight to be used for portable purposes.

Other objects, advantages, features, and uses will become more apparent as the description proceeds when considered in conjunction with the accompanying drawings, in which:

Fig. l shows a vocoder system incorporating the syn thesizer of this invention with parts illustrated schematically and certain elements thereof illustrated in elevation or in section; v

Fig. 2 shows an enlarged embodiment of the synthesizer component of Fig. 1, Without the electrical connections, looking downwardly thereon;

Fig. 3 shows an enlarged cutaway portion of the cathode, grid, and anode construction in the special tube;

Fig. 4 illustrates the light streaks formed on a cutaway v -portion of the fluorescent screen of the special tube;

unbaiiied cylindrical lens;

the analyzer and a further grid arrangement to control anew andI improved synthesizer for a vocoder system for i Fig. 7 illustrates the emitted light rays through a light baffled cylindrical lens;

Fig. 8 illustrates the action of the light streaks through the light bai-lle in the speech synthesizing position;

Fig. 9 illustrates the action of the light streaks passing through the light baffle in the rio-voice condition;

Fig. l0 shows a modified electrical arrangement with the special tube to provide a continuous spectrum;

^ Fig. ll illustrates the fluorescent pattern resulting from the arrangement used in Fig. l0;

Fig. l2 shows another modification of an electrical arrangement with the special tube to provide a continuous spectrum; and

Fig. 13 is a graph of a performance function of the disk shown in Fig. 5 in terms of variations in disk radii along the graph abscissa and of variations in flicker frequency along the ordinate.

Referring more particularly to Fig. 1, there is shown the vocoder system with the synthesizer component incorporated therein in accordance with the present invention. To the left of the first vertical dotted lines in Fig. l isv the analyzer schematically shown in which a micro phone 10 is coupled to a fundamental extraction circuit 11 that is connected through a frequency meter 12 and a band-pass filter 13 capable of passing signals of about cycles per second. The channel through the elements 11, 12, and 13 is to define the fundamental frequency of sound entering the microphone 10 by the magnitude of the signal voltage. The'output of these elements providesl the pitch and voicing signal known as the pitch channel 14.

The microphone 10 is alsocoupled to a bank of bandpass filters, .herein shown as ten to illustrate the invention although more or less maybe used, -and identified by the reference characters 15 to 24, inclusive. Each band-.pass filter is coupled through a rectifier 25 to 34, respectively, and thence through low-pass filters 35 to 44, respectively, providing the ten channel energy signals of the voice or other sound spectrum. The ten spectrum channels cover most of the voice or sound spectrum to be transmitted, each channel accounting for a frequency band, and altogether providing a spectrum of from 250 cycles per second to 30 00 cycles per second.

Referring to Figs. l to 4, in the synthesizer forming this invention, a special vacuum tube is used having a cathode 61, an anode 62, and a fluorescent screen :63 similar in some primary respects to an image convector tube. The cathode and anode construction, better seen in the enlarged portion shown in Fig. 3, comprises a photo cathode which is sensitive particularly tored light to"ei`nit electrons when uniformly illuminated by a red light (not shown). The anode 62 has elongated horizontal slits 64 therein, ten shown herein to illustrate and describe the invention, an all parallel. As may be readily understood some of the emitted electrons will strike the anode and others will shoot through the elongated slits 64 and strike the fluorescent screen 63. In order to control the electron flow through each elongated slit 64 a grid wire 65 (seen in Fig. l but best seen in Fig. 3) is looped around each elongated slot and the ends thereof of each grid extending through the glass tube envelope. The ten grids 65 are coupled to the ten spectrum channels 45 to 54, respectively, to bias the respective grids in correspondence with the respective voice frequency channel to control the intensity, or cut off, the light streak corresponding to the voice frequency channel. For reasons later to be better understood the lowermost channel 15, 25, 35, 45, 64 will be considered the lowest in frequency of the frequency channels to establish the fundamental frequency and the remainder the higher frequencies and harmonics. As an example, Figs. 3 and 4 show two electron streams passing through two elongated horizontal slits 64 and one elongated horizontal slit being blocked by reason of the grid wire being biased to cut-off. A cutaway portion of the fluorescent screen 63 corresponding to this portion of the cathode and anode is shown in Fig. 4 with the two light streaks of the two emitted light sheets, one light streak being shown less intense than the other merely to illustrate the grid control of the elongated slits 64. The cathode 61 is connected to ground at a voltage source and the anode 62 is connected to the voltage source through an adjustable resistor 66.

In order to prevent wander in the emitted electron sheets and to keep the light sheets in sharp definition on the fluorescent screen, an electromagnetic lens 70 or coil is placed over the special tube 60 for substantially its entire length to keep the emitted electron sheets in the same relative position as they are upon leaving the elongated slits 64. The electromagnetic lens or coil 70 is connected to the voltage source for the desired voltage to be impressed thereon.

Within the special tube are two electrostatic plates 72 and 73 on diametrical opposite sides, and in planes parallel to the emitted electron sheets. The plates 72 and 73 are connected to a potential above and below the potential of the cathode 61 which, in this neutral condition, will not influence the emitted electron sheets. The plate 72 of higher potential is also connected to the movable tap of a potentiometer 74 which movable tap is controlled in position by the pitch channel voltage coming by way of the conductor 14. the pitch channel conductor being connected through an amplifier 75 to a solenoid 76 operative to position the movable tap of the potentiometer in accordance with the pitch channel voltage. The potential differential between the electrostatic plates 72, 73 is thereby changed in accordance with speech pitch which is effective to raise or lower all of the emitted electron sheets uniformly for reasons which will later be apparent. As well known in the art this control could also be effected by electromagnet coils on the exterior of the tube.

In front of the special tube 60 is a system of light bales 80 lying parallel to the emitted electron sheets or the light streaks drawn thereby. Adjacent the end of the light bales 80 is a cylindrical lens 31 with the axis of curvature thereof perpendicular to the light battles 8G. In the plane of the line focus of the cylindrical lens 81 is a modulation disk 32 mounted at its axis on a shaft 33 of the motor 84. The modulation disk d2 is so positioned that a radial portion lies along the line focus of the cylindrical lens 81. The arrangement of light passages through the modulation disk 82 are shown in Fig. 5 wherein the frequency circles a1 to fno represent the ten frequency bands to synthesize speech. The lowest frequency is represented at the shortest radius and the frequency rises -as the radius becomes progressively larger This control is illustrated herein by in such a way that the frequency for a2 equals twice the frequency for a1; the frequency for a3 equals twice the frequency for a2, and so forth. The radial distances between cn and a2, a2 and as, as and a4, etc. of Fig. 5 are always equal. (See Fig. 13.) The frequency band ai, for example, represents the fundamental frequency and a2 to aio represent the higher frequencies and harmonics. Additional frequency circles lie outside the a1 to aro circles to allow raising and lowering of the whole frequency spectrum as will later be better understood. Next adjacent the modulation disk 82, and in the light path, is a condenser lens 85 that functions to concentrate all the modulated light rays onto the cathode of a photoelectric cell 86 which can receive the frequency bands of all ten frequencies produced by the ten modulated light beams from the fluorescent screen 63. The output of the photoelectric cell 86 is amplified in the amplifier 87 and passed to a sound output device 88 for use as a transmitter.

The necessity for the baille system 80 is best understood by referring to Figs. 6 and 7. As an example, several uorescent light streaks 9d are illustrated as they may appear' on the fluorescent screen 63. Without the light bales @il in Fig. 6 the light from each light streak 90 will be brought to focus at a point 91, using one light streak for example. This light streak will be refracted through lens 81 for its full length, the extreme points being shown at 92 and 93, which will produce a light streak at the focus of the cylindrical lens 81 which is perpendicular to the light streak 90. Since all the light streaks 9@ would produce superimposed light streaks 91, 92, 93, there could be no separation of the ten light channels necessary to synthesize speech or like sounds. With the baffles dit in position as shown in Fig. 7 each light streak Slt) will be made to form a spot focus, two of which are shown at 94 and 95 as examples. For synthesizing speech each light channel must be separate and distinct, the combination of all the open light channels passing through the modulating disk 82 providing the proper speech spectrum of the speaker at the microphone 1t). At the time that no speech is transmitted into the microphone 10, however, it is `desirable to have breath sounds synthesized which can be produced by a continuous light streak 91-93 falling on the modulator disk 32 to produce a continuous spectrum as hiss. To accomplish this the light baffle system Si) could be rotated sufficiently to allowl such a light streak 91-93 to be formed, but this is not practical for handling speech synthesis where very rapid changes are necessary.

To accomplish the above purpose reference is made to Figs. 1, 2, 8, and 9 where a pair of dissimilar coils 10Go and 16917 are fixed over the electromagnetic lens coil on diametrically opposite sides of the tube 60. The coils 100:1 and 100b are dissimilar to produce a nonhomogenous magnetic eld or unlike llux densities across the tube 60 to produce a bending force on the electron sheets. Upon the energization of these coils 100a and 100b the emitted electron sheets will all be substantially uniformly rotated slightly from the horizontal condition shown in dotted lines in Fig. 8 to the angular condition shown by the dotted lines in Fig. 9. The angular condition of the emitted electron sheets likewise produce angular light streaks on the fluorescent screen which pass through the light baflles as shown in Fig. 9 to produce for each channel a short vertical streak which connects the next adjacent vertical channel streak to produce a continuous vertical streak. This vertical streak lpassing through the modulation disk produces acontinuous spectrum which provides the hiss ordinarily produced by a hiss generator. The coils e and 100b are switched on and off in accordance with the voiced and unvoiced signals on the pitch channel; that is, at the time a voice signal appears in the pitch channel 14 the switching element 101 is operative to energize a solenoid, for example, to attract the switch arm 102away 4from the contact 103 to which it is biased for coupling the coils 100e and 100b in circuit with a voltage source represented by a battery although the voltage source can be from the single source shown as a voltage divider supplying all the electrical elements. During no-voice signals on the pitch channel 14 the contact 102, 103 is established to produce a hiss in the output of the system to simulate breathing.

The continuous spectrum to produce hiss may also be accomplished in other ways, one modification being shown in Fig. l where a wobble frequency generator 105 is switched in circuit with the electrostatic plates 72 and '73 in the absence of any pitch voltage signal on the pitch channel 14. The light streaks, ten or less, produced on the liuorescent screen 63 as a result of the wobble frequency being impressed on the electrostatic plates 72 and 73 produce wide bands (see Fig. 1l), one for each emitted electron sheet, which touch or are in close adjacent relation causing substantially a continuous spectrum to be produced through the modulation disk 82.

A further modification which may be used to produce a continuous spectrum is shown in Fig. l2 where the potential supply to the electromagnetic lens coil 70 may be changed by a switch 110 to switch to a low voltage causing the light streaks formed on the fluorescent screen 63 to blur giving substantially the same results as shown in Fig. ll. The switch 110 may be under the control of the pitch channel 14 and thrown in a similar manner as the wobble frequency switch in Fig. 10.

in the operation of the device voiced sounds are made into the microphone and are analyzed in the analyzer component. One code channel deiines the type of source and the fundamental frequency which is transmitted over the pitch channel 14. The voiced sounds are also impressed on the audio responsive band-pass filters 15-24 each of which segregate the energy frequency coming within its band. The energy frequency of each responding filter is rectified in the corresponding elements to 34 and smoothed out for its code channel of speech spectrum corresponding thereto.

Each code channel, 45 to 54, controls the intensity of the electron flow from the cathode 61 in the special tube 60 for the corresponding channel in this tube, channel 45 of this analyzer controlling the lowermost electron channel slit 64 in the special tube 60 by the grid 65, and so on up through the special tube electron channels. Those analyzer code channels that are not responsive to the audio frequency will produce zero voltage on the respective grids in the special tube 60 and these electron channels will be cut olf. The higher the voltage in certain of the analyzer code channels 45--54 the greater the intensity of the corresponding synthesizer channels to produce speech simulating that voiced in the microphone 10. The lower frequency channels would probably be emphasized for a mans voice while the higher frequency channels would be emphasized for a womans voice. The pitch in the voiced sounds at the microphone is controlled in the synthesizer by the pitch channel 14 control through the elements 75 and 76 to position the movable tap on the potentiometer 74 placing a potential on the electrostatic plates 72-73 to cause the emitted electron sheets to rise (as viewed in Fig. l) for higher pitches and to fall for lower pitches. The synthesized pitch differences are produced by the light streaks on the fluorescent screen in the higher positions to strike the modulation disk 82 at a greater radius which produce higher frequencies of light ray modulation. vAnd vice versa, va uniform lowering of all the light streaks on the fluorescent screen 63 causes a modulation ofthe light rays in the shorter radii of the modulation disk S2 wherein the pitch of the fundamental frequency and the other frequencies together with theA speech analyzed are focused onto the cathode of the photoelectric cell 86 where all frequency channels are converted into electric impulses` for wire or wireless transmission or into audio voiced sounds through the receiver device 88. The function of the special tube 60, the modulation disk 82, and the photoelectric cell perform the task of the relaxation oscillator, the electronic modulators, and the filters in the conventional known syntheslzer.

When there are no voiced sounds it is desirable to have hiss simulating breathing. Thus, in the present synthesizer the pitch channel 14, in the absence of speech being impressed on the microphone, carries insuiiicient voltage which allows the coils 100a and 100b to be placed in circuit to uniformly rotate the emitted electron sheets in the special tube 60, or to blur the light streaks by wobble frequency or by cutting the voltage off of the electromagnetic lens, to produce a continuous spectrum over at least part of the channels to produce a hiss sound in the synthesized output.

lt may occur to some that an easier way to produce the electron light channels in the synthesizer would be to have a single round hole in the anode 62 for each channel such that each would produce a spot on the iluorescent screen wherein the light baiiie system and cylindrical lens 81 could be eliminated. The disadvantages in this method, while practical and operative, are that the concentration of the slit 64 down to a spot greatly reduces lthe electron intensity which the -cylindrical lens 81 is able to save.

While the preferred form or forms of the synthesizer for the vocoder have been shown and described it is to be understood that many changes or modifications may be made in the constructional details and features without departing from the spirit and scope of my invention and I desire to be limited only in the scope of the appended claims.

I claim:

l. A synthesizer in a voice coder system for the artiiicial production of an audible sound spectrum comprising; vacuum tube means for producing a plurality o f vertically spaced parallel light channels controllable in intensity and controllable uniformly in angular deflection linclusive of an electron gun consisting of an electron supplying elongated cathode electrode spaced axially of the tube from .an electron accelerating anode electrode with an electron liow rate controlling grid electrode terminal for each of a plurality of sound spectrum frequency band channels input surrounding each of and controlling the flow rate of electrons through a plurality of electron conducting apertures in the anode electrode; light modulation means in the paths of said light channels for modulating said plurality of light channels into separate light frequencies corresponding to the number of light channels, said separate light frequencies all producing a light frcquency spectrum corresponding to that of the audible spectrum; and a light sensitive element in the path of all said light channels posterior to said light modulating means for receiving the modulated light frequencies and converting them into equal frequency electrical currents capable of being vtransformed into synthetic voice at a pitch corresponding to the angular detiection of the light channels and at a volume intensity of certain frequency levels corresponding to the intensity control of each light channel.

2. A synthesizer in a voice coder system for the artificial production of a sound spectrum comprising; an electrical to light energy converting vacuum tube having a cathode electrode, a multiple apertured electron beam accelerating anode electrode, and la plurality of anode aperture looping grid electrodes for producing vertically spaced parallel light channels in alignment one over the other; means for controlling the intensity of light in each light channel; means for deliecting all the -light channels uniformly up or down; .means for spreading the vlight `'in each light channel toward the next adjacent light channel; modulator means for interrupting the light in each light channel producing various frequency bands progressively from the first light channel to the last in the frequency spectrum corresponding to the audible spectrum; and light sensitive means in the path of all said light channels posterior to said modulator means for converting the light frequencies into electrical impulses capable of being produced in sound, the frequency bands being produced in volume corresponding to the means for controlling light intensity in said light channels and the pitch of the fundamental frequency corresponding to the deflection control of all said light channels whereby speech is synthesized, the non-voiced sounds being synthesized by a continuous spectrum being formed by the means for spreading the light in each light channel.

3. A synthesizer as set forth in claim 2 wherein said means for producing light channels in alignment one over the other is an electronic tube having an electron emitting cathode, grid surrounded anode with an opening for each light channel, and a lluorescent screen; said means for controlling the intensity of light in each light channel is a grid at each anode opening individually controlled in potential; said means for deilecting all the light channels uniformly is a pair of electric variably chargeable means; and said means for spreading the light in said light channels is electric potential means for influencing the electrons in said special tube.

4. A synthesizeras set forth in claim 3 wherein said modulator means is a rotatable disk with the axis thereof in a plane parallel to said light channels and a radial portion thereof in the path of said light channels and said light sensitive means is a photoelectric cell.

5. A synthesizer in a voice coder system having an analyzer pitch channel and spectrum channels for the artificial production of vocal or other sounds comprising; an electronic tube having an electron emitting photocathode, an anode plate in front of said cathode with electron passing horizontal elongated slits therein, a control grid surrounding each slit, and each slit surrounding grid gating the rate of electron flow through the slit, a pair of electrostatic plates, and a fluorescent screen, said grids each being coupled to one each of said spectrum channels to control the intensity of the electron flow through the respective` slit and Isaid electrostatic plates being connected with a power supply; a cylindrical lens in front of said electronic tube for bringing to focus each light streak on said fluorescent screen formed by electron flow through said slits; a modulator disk rotatably mounted with a radial portion thereof in the focus of said light streak; a light sensitive element posterior to said modulation disk for converting light impulses passing through said modulation disk into electrical impulses; a condenser lens for bringing the modulated light to a focus on said light sensitive element; an electron path linfluencing coil means on said electronic tube and coupled to said pitch channel for rearranging said light streaks on said fluorescent screen to produce a continuous spectrum by said modulator disk whereby vocal and other sounds analyzed are synthesized electrically for transformation into audible sounds.

6. A synthesizer as set forth in claim 5 wherein said electron path influencing means is a pair of coils exterior of said electronic tube and releasably energized from a direct current source to influence the electron flow from said slits in the absence of any signal voltage in said pitch channel.

7. A synthesizer as set forth `in claim 5 wherein said electron path influencing means is powered by output from'the pitch channel in the presence of signal voltage therein. y

8. A synthesizer in a voice coder for the artificial production of vocal and other sound comprising; cathode ray tube means with an electron intensity controlling grid surrounding each aperture in an electron accelerating anode spaced axially from an electron supplying cathode for producing a plurality. of horizontal parallel streaks of light on a fluorescent screen thereof, each parallel streak of light being produced by a beam of electrons emitted from said cathode electrode and the electrons being grid controlled in intensity by a spectrum channel voltage; an electrical lens means on said tube for bringing the electrons developing said light streaks into sharp focus on said fluorescent screen; electrical means capable of inuencing the cathode rays uniformly to divert them up or down in accordance with a potential difference applied to the cathode ray diverting electrical means; horizontal light baille means and a cylindrical lens adjacent said fluorescent screen to bring said light streaks on said fluorescent screen to a focus in a plurality of spots in a vertical plane; a modulator disk rotatable with a radial portion thereof in coincidence with the vertical focus of said cylindrical lens; a light sensitive cell posterior to said modulation disk and positioned to be struck by said spots of light; and means to elongate said spots of light to produce a continuous spectrum by said modulator disk whereby a voice spectrum can be synthesized in pitch by said electrical means in accordance with a pitch signal voltage and unvoiced sounds can be simulated by said continuous spectrum.

9. A synthesizer as set forth in claim 8 wherein said means to elongate said spots is releasably powered from a direct current source.

l0. In .a synthesizer having a rotatable ilash frequency determining light modulation disk and a photoelectrc cell to receive modulated light signals from the disk for conversion into an electrical frequency spectrum, means providing a pitch signal voltage, an electronic tube comprising; a tube envelope having a fluorescent surface at one end thereof, an electron multiple stream uniformly emitting cathode at the other end thereof, an anode between said cathode and said fluorescent surface and having a plurality of grid looped horizontal parallel slits therein to permit a plurality of sheets of electron flow through said slits to form horizontal luminous light streaks on said fluorescent surface corresponding to electrical spectrum channels, and a control grid gating the intensity of the electron llow through each anode slit and each control grid adapted to be coupled to a spectrum control channel voltage to control the intensity of said respective luminous streak; electrical lens means positioned circumferentially outwardly of said tube for maintaining the relative positions of the sheets of electrons passing through the electronic tube and maintaining sharp focus of said luminous streaks; electron influencing means Within said tube for uniformly controlling the vertical position of said luminous streaks in accordance with a pitch signal voltage; and electron dellecting means mounted on said tube for shifting the sheets of electrons Within the tube prior to their arriving at the tube screen for display as said luminous streaks switchable to an inactive position in accordance with the existence of pitch signal voltage whereby said luminous streaks form light channels interrupted by said modulation disk into separate audio frequency bands at a fundamental pitch established by said electron influencing means for voiced synthesis and said luminous streaks are shifted to produce a continuous spectrum when interrupted by said modulation disk for unvoiced synthesis picked up for conversion by the photo-electric cell.

11. In a synthesizer having a rotatable light modulation disk and a photo-electric cell to receive modulated light signals for conversion into a sound frequency spectrum, an electronic tube comprising, a tube envelope having a fluorescent surface at one end thereof, a uniformly emitting cathode at the other end thereof, an

Ianode between said cathode and said fluorescent surface and having a plurality of horizontal parallel slits therein to permit electron ow through said slits to form corresponding horizontal luminous streaks on said fluorescent surface corresponding to spectrum channels, a control grid surrounding each slit and each adapted to be coupled to a spectrum control voltage to control the intensity of said respective luminous streak, electron inuencing means within said tube for uniformly controlling the vertical position of said luminous streaks corresponding to changes in pitch, and electron deecting means without said tube for rearranging said luminous streaks at times corresponding to unvoiced sounds whereby modulated light channels to the photo-electric cell are controllable to effect changes corresponding to pitch, to frequencies of the sound spectrum having the greatest intensity, and to unvoiced speech sounds.

12. In a synthesizer as set forth in claim 11 wherein said electron influencing means and said electron deecting means are electromagnetic means and electrostatic means respectively.

13. A method of synthesizing voiced or other audible sounds in a voice coder system comprising, producing a plurality of vertically spaced parallel sheets of light rays corresponding in number to a plurality of spectrum channels and grid controlling the intensity of each of said light rays in accordance with a corresponding spectrum channel, frequency modulating said light rays, converting said modulated light rays into electrical impulses suitable for reproducing in audible sound, shifting said light rays uniformly anterior to modulation corresponding to changes in pitch, and detlecting said light rays anterior to modulation at times corresponding to nonexistent sounds.

14. A method of synthesizing voiced or other audible sounds in a voice coder system comprising, producing electron flow in a plurality of parallel vertically spaced horizontal planes corresponding in number to a plurality of spectrum channels, grid controlling each horizontal plane of electrons in intensity of electron llow, shifting all horizontal planes of electron ow uniformly in a vertical direction in accordance with changes in pitch, deflecting said horizontal planes of electrons at times corresponding to silent periods, imaging said horizontal planes of electrons on a uoresceut screen into horizontal light streaks, baiiling said horizontal light streaks in continuing horizontal light channels, concentrating said light streaks each to a point of light in each of said light channels in vertical relation, modulating said light channels at said vertical points of light in frequency bands providing an audio frequency spectrum, and converting said modulated light channels into electrical impulses suitable for reproduction into audible sound.

l5. A voice coder-system, comprising an analyzer section and a synthesizer section collectively reproducing sound energy as a visually perceptible recording, the analyzer section comprising a sound energy receiving means converting sound energy into electrical energy, means subdividing and channeling by frequency bands the electrical energy output from said sound energy receiving means including a pitch controlling pitch channel conducting pitch and voicing signal as a fundamental frequency and a plurality of spectrum channels of individually discrete frequency bands providing output from the analyzer section and input into the synthesizer section, and the synthesizer section comprising a vacuum tube containing an electron emitting elongated cathode electrode, a plurality of vertically superimposed grid electrodes to which the separate outputs from the spectrum channels are severally applied, an electron accelerating anode electrode defining a plurality of grid looped anode apertures for the passage therethrough of electron beams of intensities controlled selectively and individually by said grid electrodes, a tube screen converting the vertically spaced and parallel tube electron beams into light energy presentations, light baille means selectively conducting as vertically spaced and parallel light streaks the light energy presentations on the tube screen, cylindrical lens means directing the light streaks conducted by the bale to a spot focus, a driven light modulation disk imparting light ash frequencies to the light spot foci, condenser lens means condensing the light flash frequencies, photoelectric cell means provided with a cathode electrode target for the light flash frequencies condensed by said condenser lens, and sound recording means receiving the photoelectric cell output in substantially reproducing as a visually perceptible recording the sound energy from the sound source.

References Cited in the file of this patent UNITED STATES PATENTS 2,500,431 Potter Mar. 14, 1950 2,516,752 Carbrey July 25, 1950 2,517,102 Flory Aug. l, 1950 OTHER REFERENCES Speech and Communication Problems, rl-echnology Review, pages -146, vol. 54, issue 3, January 1952. 

